One Design issues aside, has anyone considered (or accomplished) moving the spinnaker hoist up 2-3 feet? I have seen some J/29FR with this configuration before.

We have discussed mastehead kites here at some length and it is risky with an unsupported mast head, but 2-3 feet above the shrouds should yield enough strength.

An external halyard would be easiest; it was suggested to me to use a fixed spnnaker pole ring riveted up there to mount the block but if there are other suggestions I am all ears. If it is successful, an additional lightweight sheeve box could be installed later.